| Md. Wasim Aktar | | | | 2. US EPA. 2000. Reregistration eligibility science |
| Pesticide Residue Laboratory, Department of | | | | chapter forchlorpyrifos. Fate and environmental |
| Agricultural Chemicals, Bidhan Chandra Krishi | | | | risk assessment chapter(Revised June). |
| Viswavidyalaya, Mohanpur-741252, Nadia, West | | | | chlorpyrifos/efedrra1.pdf. |
| Bengal, India | | | | 3. Cox, C. 2000. Lethal lawns: diazinon use |
| Introduction Pesticides are found as common | | | | threatens salmonsurvival. Journal of Pesticide |
| contaminants in soil, air, and water, and on | | | | Reform 20(2). 2-7.72. U.S. EPA. Office of |
| non-target vegetation in our urban landscapes. | | | | Prevention, Pesticides, and Toxic Substances. |
| Once there, they can harm plants and animals | | | | 1996. Reregistration eligibility decision |
| ranging from beneficial soil microorganisms and | | | | (RED):trifluralin. Washington, D.C., April. |
| insects, non-target plants, fish, birds, and other | | | | 4. Koyama, J. 1996. Vertebral deformity |
| wildlife. Table 1 summarizes the harmful effects to | | | | susceptibilities ofmarine fishes exposed to |
| non-target organisms of some commonly used | | | | herbicide. Bull. Environ. Contam. Toxicol. 56:655-662. |
| urban herbicides. | | | | 5. Extoxnet. 1996. Pesticide Information Profile: |
| Table 1 . Harmful effects of selected herbicides on | | | | oryzalin. June. |
| non-target organisms Source: Sanders, 1969 | | | | 6. Shafiei, T.M., and H.H. Costa. 1990. The |
| Fish When pesticides contaminate water they can | | | | susceptibility andresistance of fry and fingerlings |
| be harmful to the fish that live there. Insecticides | | | | of Oreochromis mossambicus Peters to some |
| can be particularly toxic to fish. Chlorpyrifos, a | | | | pesticides commonly used in Sri Lanka. Journal |
| common contaminant of urban streams,18 is very | | | | Appl. Ichthyol . 6:73-80. |
| highly toxic to fish, and has caused fishkills in | | | | 7. Folmar, L.C., H.O. Sanders, and A.M. Julin. 1979. |
| waterways near treated fields or buildings.1,2 | | | | Toxicity of the herbicide glyphosate and several |
| Diazinon, also commonly found in urban | | | | of its formulations to fish and aquatic |
| streams,18 is acutely toxic to many species of | | | | invertebrates. Arch. Environ. Contam. Toxicol. |
| fish, including salmon.3 Herbicides can also be toxic | | | | 8:269-278. |
| to fish. According to the EPA, studies show that | | | | 8. Morgan, J.D. et al. 1991. Acute avoidance |
| trifluralin, an active ingredient in the weed-killer | | | | reactions and behavioral responses of juvenile |
| Snapshot, "is highly to very highly toxic to both | | | | rainbow trout ( Oncorhynchus mykiss) to Garlon |
| cold and warmwater fish."4 It was also shown in | | | | 4, Garlon 3A, and Vision herbicides. Environ |
| a series of different tests to cause vertebral | | | | Toxicol. Chem. 10:73-79. |
| deformities in fish.5 Oryzalin, the active ingredient | | | | 9. Liong, P.C., W.P. Hamzah, and V. Murugan. 1988. |
| of Surflan, also is 'highly toxic' to fish.6 The | | | | Toxicity of some pesticides towards freshwater |
| weed-killers Ronstar and Roundup are also acutely | | | | fishes. Malaysian Agric. J. 54(3):147-156. |
| toxic to fish.7,8 The toxicity of Roundup is likely | | | | 10. McBride, J.R., H.M. Dye, and E.M. Donaldson. |
| due to the high toxicity of one of the inert | | | | 1981. Stress response of juvenile sockeye salmon |
| ingredients of the product. In addition to direct | | | | ( Oncorhynnchus nerka) to the butoxyethanol |
| acute toxicity, some herbicides may produce | | | | ester of 2,4-dichlorophenoxyacetic acid. Bull. |
| sublethal effects on fish that lessen their chances | | | | Environ. Contam. Toxicol. 27:877-884. |
| for survival and threaten the population as a | | | | 11. Little, E.E. 1990. Behavioral indicators of |
| whole. Glyphosate or glyphosate-containing | | | | sublethal toxicity of rainbow trout. Arch. Environ. |
| products can cause sublethal effects such as | | | | Contam. Toxicol. 19:380-385. |
| erratic swimming and labored breathing which | | | | 12. Zaffaroni, N.P. et al. 1986. The toxicity of 2,4- |
| increase the fish's chance of being eaten.9,10 | | | | dichlorphenoxyacetic acid to the adult crested |
| 2,4-D herbicides caused physiological stress | | | | newt. Environ. Res. 41:79-87. |
| responses in sockeye salmon,11 and reduced the | | | | 12. Suwalsky, M. et al. 1999. Toxic action of the |
| food gathering abilities of rainbow trout.12 | | | | herbicide 2,4-D on the neuroepithelial synapse and |
| Other Aquatic Animals and Plants In addition to | | | | on the nonstimulated skin of the frog |
| fish, other marine or freshwater animals are | | | | Caudiverbera caudiverbera. Bull. Environ. Contam. |
| endangered by pesticide contamination. 2,4- D or | | | | Toxicol. 62:570-577. |
| 2,4-D containing products have been shown to be | | | | 14. Caldwell, R.S. et al. 1979. Toxicity of the |
| harmful to newts,13 frogs,14 crabs,15 shellfish,16 | | | | herbicides 2,4-D, DEF, propanil and trifluralin to the |
| and other aquatic species.17,18 The weed-killer | | | | Dungess crab Cancer magister. Arch. Environ. |
| trifluralin is moderately to highly toxic to aquatic | | | | Contam. Toxicol. 8:383-396. |
| invertebrates, and highly toxic to estuarine and | | | | 15. Cheney, M.A., R. Fiorillo, and R.S. Criddle. 1997. |
| marine organisms like shrimp and mussels. Diuron | | | | Herbicide and estrogen effects on the metabolic |
| is also highly toxic to aquatic invertebrates.19 | | | | activity of Elliptio complanata measured by |
| Since herbicides are designed to kill plants, it | | | | calorespirometry. Comp. Biochem. Physiol. |
| makes sense that herbicide contamination of | | | | 118C:159-164. |
| water could have devastating effects on aquatic | | | | 16. U.S. EPA. Office of Pesticide and Toxic |
| plants. In one study, oxadiazon was found to | | | | Substances. Office of Pesticide Programs.1989. |
| severely reduce algae growth.20 Algae is a staple | | | | Pesticide factsheet: 2,4-dichlorophenoxyacetic acid. |
| organism in the food chain of aquatic ecosystems. | | | | Washington D.C., Sept. |
| Studies looking at the impacts of the herbicides | | | | 17. Sanders, H.O. 1969. Toxicity of pesticides to |
| atrazine and alachlor on algae and diatoms in | | | | the crustacean Gammarus lacustris. Technical |
| streams showed that even at fairly low levels, | | | | Papers of the Bureau of Sport Fisheries and |
| the chemicals damaged cells, blocked | | | | Wildlife No. 25. US Dept. of Interior Fish and Wildlife |
| photosynthesis, and stunted growth in varying | | | | Service, Washington D.C. (Jan.) |
| ways.20 Another important class of organisms is | | | | 18. Extoxnet. 1996. Pesticide Information Profile: |
| the cyanobacteria. Cyanobacteria live in aquatic | | | | diuron. June. |
| environments as well as soil, and play a crucial role | | | | 19. Ambrosi, D., A. Isensee, and J. Macchia. 1978. |
| in nitrogen fixation, helping plants convert | | | | Distribution of oxadiazon and phoslone in an |
| atmospheric nitrogen into nitrate compounds that | | | | aquatic model ecosystem. American Chemical |
| the plant can use. Trifluralin was found to inhibit | | | | Society 26(1):50-53. |
| the growth of two common cyanobacteria at all | | | | 20. U.S. Water News Online. 2000. Ecologist says |
| levels of application.21 | | | | effect of herbicides on aquatic environment needs |
| Insects and Spiders In addition to killing insect | | | | research. July. tecosay7.html. |
| "pests," insecticides obviously have the potential | | | | 21. Kobbia, I. A., et al. 1991. Growth criteria of two |
| to harm non-target insects such as beneficial | | | | common cyanobacteria isolated from Egyptian |
| natural predators and pollinators. Less obviously, | | | | flooded soil, as influenced by some pesticides. |
| weed-killers can also be harmful to beneficial | | | | Water, Air, and Soil Pollution 60:107-116. |
| insects. One study found that exposure to freshly | | | | 22. Hassan, S.A. et al. 1988. Results of the fourth |
| dried Roundup (glyphosate) killed over 50 percent | | | | joint pesticidetesting programme carried out by |
| of three species of beneficial insects: a parasitoid | | | | the IOBC/WPRS-Working Group "Pesticides and |
| wasp, a lacewing and a ladybug. Over 80 percent | | | | Beneficial Organisms." J. Appl. Ent. 105:321-329. |
| of a fourth species, a predatory beetle was | | | | 23. Extoxnet. 1996. Pesticide Information Profile: |
| killed."22 Moderate doses of the herbicide 2,4-D | | | | 2,4-D. June. |
| severely impaired honeybee brood production. 23 | | | | 24. Washington State Department of |
| The herbicide oxadiazon is also toxic to bees, | | | | Transportation. 1993. Draft roadside vegetation |
| which are pollinators.24 Herbicides may hurt | | | | management environmental impact statement, |
| insects or spiders indirectly as well, such as when | | | | appendix B, B2-10. |
| they destroy the foliage that these animals need | | | | 25. Asteraki, E.J., C.B. Hanks, and R.O. Clements. |
| for food and shelter. For example, spider and | | | | 1992. The impact of the chemical removal of the |
| carabid beetle populations declined when 2,4-D | | | | hedge-based flora on the community structure of |
| applications destroyed their natural habitat.25 Birds | | | | carabid beetles (Col. Carabidae) and spiders |
| The insecticide diazinon is notorious for causing | | | | (Araneae) of the field and hedge bottom. J. Appl. |
| bird kills. Over 50 incidents involving the deaths of | | | | Ent. 113:398-406. |
| up to 1000 birds have been documented in every | | | | 26. US EPA. 1988. Diazinon; Ciba-Geigy |
| region of the U.S.95 Diazinon is so lethal to birds | | | | Corporation, et al., petitioners. Federal Register |
| that the EPA estimates that between 15 and 80 | | | | 53(65):11119-11131. (April 5). 27. US EPA. 1998. |
| minutes of grazing on diazinon treated turf is | | | | R.E.D. facts rodenticide cluster. Office of |
| enough to kill a bird.26 Non-target birds may also | | | | Prevention, Pesticides, and Toxic Substances |
| be killed if they ingest poisoned grains set out as | | | | (July). |
| bait for pigeons and rodents.27, 28 Avitrol, a | | | | 28. Extoxnet. 1996. Pesticide Information Profile: |
| commonly used pigeon bait, poses a large | | | | 4- Aminopyridine. June. pips/4-aminop.htm. |
| potential for ingestion by non target grain feeding | | | | 29. Duffard, R., L. Traini, and A. Evangelista de |
| birds. It can be lethal to small seed-eating birds.29 | | | | Duffard. 1981. Embryotoxic and teratogenic |
| rodifacoum, a common rodenticide, is highly toxic | | | | effects of phenoxy herbicides. Acta Physiol. |
| to birds. It also poses a secondary poisoning | | | | Latinoam. 31:39-42. 30. Lutz, H. and Y. |
| hazard to birds that may feed on poisoned | | | | Lutz-Ostertag. 1972. The action of different |
| rodents.30 Herbicides can also be toxic to birds. | | | | pesticides on the development of bird embryos. |
| lthough trifluralin was considered "practically | | | | Adv. Exp. Med. Biol. 27:127-150. |
| nontoxic to birds" in studies of acute toxicity, | | | | 31. MacKinnon, D.S. and B. Freedman.1993. Effects |
| birds exposed multiple times to the herbicide | | | | of silvicultural use of the herbicide glyphosate on |
| experienced diminished reproductive success in | | | | breeding birds of regenerating clearcuts in Nova |
| the form of cracked eggs. Exposure of eggs to | | | | Scotia, Canada. J. Appl. Ecol. 30(3):395-406. |
| 2,4-D reduced successful hatching of chicken | | | | 32. Marx, J et al. 1999. The relationship between |
| eggs,33 and caused feminization or sterility in | | | | soil and water, how soil amendments and |
| pheasant chicks.31 Herbicides can also adversely | | | | compost can aid in salmon recovery. Soils for |
| effect birds by destroying their habitat. | | | | Salmon 1-18. 33. Savonen, C. 1997. Soil |
| Glyphosate treatment in clear cuts caused | | | | microorganisms object of new OSU service. Good |
| dramatic decreases in the populations of birds that | | | | Fruit Grower. 1995/6other.html. |
| had lived there.32 | | | | 34. Pell, M., B. Stenberg, and L. Torstensson. 1998. |
| Beneficial Soil Microorganisms One spoonful of | | | | Potential denitrification and nitrification tests for |
| healthy soil has millions of tiny organisms including | | | | evaluation of pesticide effects in soil. Ambio |
| fungi, bacteria, and a host of others. These | | | | 27:24-28. |
| microorganisms play a key role in helping plants | | | | 35. Santos, A. and M. Flores. 1995. Effects of |
| utilize soil nutrients needed to grow and thrive. | | | | glyphosate on nitrogen fixation of free-living |
| Microorganisms also help soil store water and | | | | heterotrophic bacteria. Lett. Appl. Microbiol. |
| nutrients, regulate water flow, and filter | | | | 20:349-352. |
| pollutants.34 The heavy treatment of soil with | | | | 36. Moorman, T.B. et al. 1992. Production of |
| pesticides can cause populations of beneficial soil | | | | hydrobenzoic acids by Bradyrhizobium japonicum |
| microorganisms to decline. According to soil | | | | strains after treatment with glyphosate. J. Agric. |
| scientist Dr. Elaine Ingham, "If we lose both | | | | Food Chem. 40:289-293. |
| bacteria and fungi, then the soil degrades. Overuse | | | | 37. Fabra, A., R. Duffard, and A. Evangelista de |
| of chemical fertilizers and pesticides have effects | | | | Duffard. 1997. Toxicity of |
| on the soil organisms that are similar to human | | | | 2,4-dichlorophenoxyacetic acid in pure culture. Bull. |
| overuse of antibiotics. Indiscriminate use of | | | | Environ. Contam. Toxicol. 59:645-652. |
| chemicals might work for a few years, but after | | | | 38. Arias, R.N. and A. Fabra de Peretti. 1993. |
| awhile, there aren't enough beneficial soil | | | | Effects of 2,4- dichlorophenoxyacetic acid on |
| organisms to hold onto the nutrients."35 For | | | | Rhizobium sp. growth and characterization of its |
| example, plants depend on a variety of soil | | | | transport. Toxicol. Lett. 68:267-273. |
| microorganisms to transform atmospheric | | | | 39. Singh, J.B. and S. Singh. 1989. Effect of |
| nitrogen into nitrates that plants can use. Common | | | | 2,4-dichlorophenoxyacetic acid and maleic |
| landscape herbicides disrupt this process: triclopyr | | | | hydrazide on growth of bluegreen algae |
| inhibits soil bacteria that transform ammonia into | | | | (cyanobacteria) Anabaena doliolum and Anacystis |
| nitrite36; glyphosate reduces the growth and | | | | nidulans. Sci. Cult. 55:459-460. |
| activity of both free-living nitrogen-fixing bacteria | | | | 40. Tözüm-Çalgan, S.R.D. and S. |
| in soil37 and those that live in nodules on plant | | | | Sivaci-Güner. 1993. Effects of 2,4-D and |
| roots38; and 2,4-D reduces nitrogen fixation by | | | | methylparathion on growth and nitrogen fixation in |
| the bacteria that live on the roots of bean | | | | cyanobacterium, Gloeocapsa. Intern. J. Environ. |
| plants,39,40 reduces the growth and activity of | | | | Stud. 23:307-311. |
| nitrogen-fixing blue-green algae, 41,42 and inhibits | | | | 41. Martens, D.A. and J.M. Bremner. 1993. Influence |
| the transformation by soil bacteria of ammonia | | | | of herbicides on transformations of urea nitrogen |
| into nitrates.43,44 Mycorrhizal fungi grow with the | | | | in soil. J. Environ. Sci. Health B 28:377-395. |
| roots of many plants and aid in nutrient uptake. | | | | 42. Frankenberger, W.T., Jr. and M.A. Tabatabai. |
| These fungi can also be damaged by herbicides in | | | | 1991. Factors affecting L-asparaginase activity in |
| the soil. One study found that oryzalin and | | | | soils. Biol. Fert. Soils 11:1- 5. |
| trifluralin both inhibited the growth of certain | | | | 43. Bakalivanov, D. and O. Kostov. 1981. Soil |
| species of mycorrhizal fungi.45 Roundup has been | | | | microbiological assessment of toxicity of |
| shown to be toxic to mycorrhizal fungi in | | | | alkanoate, amide and other herbicides. Acta |
| laboratory studies, and some damaging effects | | | | Microbiol. Acad. Sci. Hung. 28:141-146. |
| were seen at concentrations lower than those | | | | 44. Beyrle, H.F. et al. 1995. Colonization of Orchis |
| found in soil following typical applications. 46,47 | | | | morio protocorms by a mycorrhizal fungus: |
| Triclopyr was also found to be toxic to several | | | | effects of nitrogen nutrition and glyphosate in |
| species of mycorrhizal fungi,48 and oxadiazon | | | | modifying the responses. Can. J. Bot. 73:1128-1140. |
| reduced the number of mycorrhizal fungal | | | | 44. Jofré, E. et al. 1996. |
| spores.49 | | | | 2,4-Dichlorophenoxyacetic acid affects the |
| Conclusion Pesticides have contaminated almost | | | | attachment of Azospirillum brasilense Cd to maize |
| every part of our environment. Pesticide residues | | | | roots. Toxicol. 107:9-15. |
| are found in soil and air, and in surface and ground | | | | 45. Kelley, W.D. and D.B. South. 1978. In vitro |
| water across the nation, and urban pesticide uses | | | | effects of selected herbicides on growth and |
| contribute to the problem. Pesticide contamination | | | | mycorrhizal fungi. Weed Science Society of |
| poses significant risks to the environment and | | | | America Meeting . Auburn University, Auburn, |
| non-target organisms ranging from beneficial soil | | | | Alabama. Pg. 38. |
| microorganisms, to insects, plants, fish, and birds. | | | | 46. Estok, D., B. Freedman, and D. Boyle. 1989. |
| Contrary to common misconceptions, even | | | | Effects of the herbicides 2,4-D, glyphosate, |
| herbicides can cause harm to the environment. In | | | | hexazinone, and triclopyr on the growth of three |
| fact, weed killers can be especially problematic | | | | species of ectomycorrhizal fungi. Bull.Environ. |
| because they are used in relatively large volumes. | | | | Contam. Toxicol. 42:835-839. |
| The best way to reduce pesticide contamination | | | | 47. Chakravarty, P. and S.S. Sidhu. 1987. Effects |
| (and the harm it causes) in our environment is for | | | | of glyphosate, hexazinone and triclopyr on in vitro |
| all of us to do our part to use safer, non-chemical | | | | growth of five species of ectomycorrhizal fungi. |
| pest control (including weed control) methods. | | | | European Journal of Forest Pathology 17:204-210. |
| References: | | | | 48. Moorman, T.B. 1989. A review of pesticide |
| 1. Cooperative Extension Service Pesticide | | | | effects on microorganisms and microbial |
| Information Project.1993. Extoxnet: Chlorpyrifos. | | | | processes related to soil fertility. Journal Prod. |
| Corvallis, Oregon: Oregon State University | | | | Agric. 2(1): 14-23. |
| (September). | | | | |